1. Field of the Invention
The present invention relates to a shift lever assembly adapted for use in a power transmission of an automotive vehicle.
2. Description of the Prior Art
As disclosed in Japanese Utility Model Publication Nos. 62-162719 and 63-49764, a conventional shift lever assembly for a power-transmission is composed of a tubular lever member rotatably mounted at its lower end on a support block secured to a vehicle body structure to be moved in a fore and aft directions and connected to a shift arm of the power transmission by means of a connecting linkage, an operation knob connected to the upper end of the tubular lever member, and a detent mechanism provided within an internal bore of the lever member to releasably restrict movement of the lever member with respect to the support block. When the detent mechanism is released by operation of the operation knob, the level member can be moved forwards or backwards to shift the power transmission.
The operation knob has a grip portion connected to the upper end of the lever member, the grip portion being formed therein with a lateral cavity opening outwardly at one side thereof and containing the upper end of an operation rod of the detent mechanism therein, an operation button slidably disposed within the lateral cavity of the grip portion, the operation button being exposed outwardly at its one end and engaged with the upper end of the operation rod at its other end, and a spring assembled within the lateral cavity to bias the operation button outwardly. In operation of the operation knob, the operation button is pushed inwardly against the biasing force of the spring to move the operation rod downward. Thus, the detent mechanism is released by downward movement of the operation rod to permit forward or backward movement of the lever member.
In the operation knob, the engagement portion of the operation button with the upper end of the operation rod is formed with an inclined cam surface on which the operational effort or force applied to the button in the lateral direction is converted into a downward force for movement of the operation rod. Accordingly, lateral movement of the operation button causes sliding movement of the inclined cam surface relative to the upper end of the operation rod. This results in an increase of the load acting on the operation button. Although the operation button is slidably assembled within the grip portion, it is difficult to provide the operation button with sufficient sliding surfaces in the grip portion. This results in unwanted movements of the operation button in operation.